Stereo camera arrangement in a motor vehicle

ABSTRACT

A stereo camera system in a motor vehicle, in particular for classifying objects and determining distance. In order to ensure secure installation and precise positioning of the camera system, in particular fixing of its lateral position, the camera system is provided with at least two camera modules, and a mount, in which camera modules are installed at a specified lateral distance apart, the mount being cemented to the inside of the windshield.

FIELD OF THE INVENTION

The present invention relates to a stereo camera system in a motorvehicle, in particular for classifying objects.

BACKGROUND INFORMATION

Stereo camera systems or stereo front-camera systems (SFK systems), inwhich two camera modules, generally parallel to one another, whichdetect the roadway area in front of the vehicle through the windshield,are mounted in the motor vehicle, are used for classifying objects on aroadway, for assigning attributes to objects, and for determining thedistance of objects from a motor vehicle. For the required accuracy indetermining the distance of contours in the stereo video image fordistances greater than/equal to 40 m, the relative positions of thecontours must be resolved into the micrometer range on the electronicimaging chips. To do this, the relative positioning of the two camerasto one another must be effected in a very precise and stable manner; inaddition, the position of the camera system with respect to the vehiclemust also be defined in a precise and stable manner at any given time.

For this purpose, a support, for example a diecasting of aluminum ormagnesium, is mounted in the roof structure of the vehicle, whichaccommodates the camera modules in accommodating regions and the controland analyzing electronics in a central region. In addition, the supportseals the optical path of the camera against soiling and scattered lightand permits simpler installation of the camera system in the process ofmanufacture.

In such conventional stereo camera systems in a motor vehicle, however,changes in spacing of the camera modules with respect to one another andwith respect to the motor vehicle are a problem. Changes in spacing thattake place slowly, due for example to thermal expansion of the support,may be compensated for by readjustment of image correction data. Forthis purpose, the required parameters may be detected by a separatesensor system or may be determined directly from the image processingsystem.

On the other hand, brief changes in spacing, which may for example beinjected into the support by vibrations, can generally not be corrected.The support system must therefore have a high degree of rigidity to allvibrations under the video frequency—generally 30 Hz–100 Hz, dependingon the system. However, more rigid design of the support generallyresults in higher manufacturing costs and a higher total weight and yetfails to provide sufficient suppression of vibrations.

SUMMARY OF THE INVENTION

In contrast, the stereo camera system according to the present inventionhas the advantage in particular that reliable and precise setting of theposition of the camera modules, in particular their relative position toone another, is possible with relatively little expenditure andadvantageously low manufacturing costs, low mass and low spacerequirement.

The present invention is based on the idea of utilizing the highresistance to deformation or even freedom from deformation of thewindshield for stable alignment of the camera modules of the stereocamera system. To this end, the camera modules are accommodated in amount that is cemented directly to the inside of the windshield. Due tothis fastening, injection of vibrations of the sheet metal parts of thebody into the camera system is at least greatly suppressed in the camerasystem. At the same time, the mount advantageously is free from anymechanical connection to the roof of the vehicle. Here the sensor systemmay be covered or sealed off from the rest of the interior of thevehicle by for example an additional cover, installed between thewindshield and the roof region, which is not in contact with the mount.Data lines and power supply lines are provided between the cameramodules and a control means for control and optionally analysis. In thisconnection, the control means may be fastened in an independent housingin the vehicle roof, so that the total mass of the camera systemcemented to the windshield is small. At the same time, injection ofvibrations via the data lines and power supply lines is negligible andmay be minimized by using flexible lines.

According to the present invention, a one-piece mount may beadvantageously used, so that the relative distance of the two cameramodules is specified and fixed by the rigid design of the mount. In thisconnection, the material of the mount advantageously has a coefficientof thermal expansion similar to that of the glass material of thewindshield, so that the development of stresses and loosening of thecementing connection is prevented. This material may in particular be asynthetic material that advantageously has a low weight and thus doesnot substantially increase the total mass of the camera system cementedto the windshield.

Alternatively to the use of a one-piece mount, the use of a mount havingtwo separate parts, each of which surrounds a camera module and isfastened to the windshield by cementing, is also possible. Here themount parts seal off the space in front of the lens between the cameramodules and may for example be cemented accurately to the windshield byan automated handling procedure.

In order to prevent the development of excessively high pressuredifferences between the space in front of the lens within the mount andthe surrounding camera region of the cover, a pressure equalizing devicemay be provided in the mount in all embodiments. This may be done by forexample an elastic, for example bellows-like, region, or advantageouslyby a gas-permeable and moisture- and dirt-impermeable region, forexample a semi-permeable membrane of a suitable textile material, forexample microfiber material.

According to the present invention, lifelong sealing of the space infront of the lens against dust and moisture and protection fromscattered light may in particular be obtained.

The mechanical stress of the cementing surfaces between the mount andthe windshield due to auto body deformations, which occur with the useof a rigid supporting system mounted in the roof region, are absent inthe system according to the present invention.

In this connection, according to the present invention, rapid, simpleand secure assembly is made possible in that the camera modules arefirst inserted into the mount. For this purpose a snap-in or snap-fitmechanism may for example be provided in the mount for accommodation ofthe camera modules, in for example their lens region, in order to ensuresecure positioning and firm seating. The mount with the camera modulesin place is then cemented to the inside of the windshield. These stepsmay be executed immediately after production of the windshield, forexample in the windshield production shops, so that the windshieldtogether with the camera system composed of camera modules and mount canbe delivered as one structural unit. After insertion of the windshieldinto the body, electrical connection of the camera modules, inparticular data connection with the control means via a flexible dataline, and installation of the cover between windshield and roof regiontake place.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section through a stereo camera systemaccording to one embodiment of the invention.

FIG. 2 shows a cross section through the system of FIG. 1.

FIG. 3 shows a perspective view of a mount according to the presentinvention.

DETAILED DESCRIPTION

FIG. 1 shows, as a partial view of a motor vehicle, an upper region ofwindshield 10, which is connected by a seal 15 with a roof section 20 ofthe vehicle. A cover 30 is provided between the inside 11 of windshield10 and roof section 20 and encloses a camera region 35. Provided incamera region 35 is a mount 40, which is fastened to the inside 11 ofwindshield 10 in cementing regions 45 by a cementing layer 46. Accordingto FIGS. 1, 2, mount 40 does not rest against cover 30. Mount 40 holdstwo camera modules 50, essentially parallel to one another, at aspecified distance apart, a space 47 in front of the lens being formedbetween each camera module 50 and windshield 10, in order not toinfluence the optical path in front of the camera modules. Cementingregions 45 advantageously extend annularly about spaces 47, in front ofthe lenses so that mount 40 covers the camera modules at the bottom andat the sides and thus keeps scattered light away from camera modules 50.According to FIGS. 2, 3, the mount may for this purpose have closedrecesses 42, in which according to FIG. 2 a round recess or according toFIG. 3 a rectangular recess 44 is formed for secure installation of thecamera modules. Lateral positioning of recesses 42 with respect to oneanother is ensured by crosspiece 43. The front of crosspiece 43 mayalternatively also serve as cementing region for fastening to the inside11 of windshield 10. The recesses in mount 40 may be designed, accordingto FIG. 1, with a uniform cross section in the longitudinal directionor, according to FIG. 3, with a tapering cross section for fixing cameramodules 50 in the longitudinal direction.

The power supply of camera modules 50 and input of the data of cameramodules 50 are provided by one or two printed circuit boards 60 on theback of camera modules 50, while flexible cables, not shown, for thepower supply and the data line run from the printed circuit boards 60 toa control means outside cover 30.

1. A stereo camera system in a motor vehicle having a windshield, thestereo camera system comprising: at least two camera modules; and amount in which the camera modules are situated at a preselected lateraldistance apart, the mount being cemented to an inside of the windshield,wherein the mount is one piece and has two mounting regions, each ofwhich holds one of the camera modules and is rigidly connected to theother by a crosspiece, and wherein the front of the crosspiece serves asa cementing region for fastening to the inside of the windshield, andwherein contact surfaces of the mount are sealed off on the inside ofthe windshield by a permanently elastic seal.
 2. The stereo camerasystem according to claim 1, wherein the stereo camera system is forclassifying objects.
 3. The stereo camera system according to claim 1,wherein the the two mounting regions are cemented to the inside of thewindshield at a preselected lateral distance from the other.
 4. Thestereo camera system according to claim 1, wherein spaces are formed infront of lenses between the camera modules and the windshield.
 5. Thestereo camera system according to claim 4, wherein the mount is cementedon the inside of the windshield in cementing regions around the spacesin front of a lens.
 6. The stereo camera system according to claim 1,wherein the camera modules are connected together by an assembly supportthat is situated separate from the mount.
 7. The stereo camera systemaccording to claim 1, wherein a material of the mount has a coefficientof thermal expansion that substantially corresponds to a coefficient ofthermal expansion of the windshield.
 8. The stereo camera systemaccording to claim 7, wherein the material is a synthetic material. 9.The stereo camera system according to claim 1, further comprising acover affixed to the windshield and a roof section of the vehicle andsurrounding a camera region in which the mount is provided including thecamera modules.
 10. The stereo camera system according to claim 1,further comprising a printed circuit board for data capture and powersupply of the camera modules, situated on a back of the camera modules.11. The stereo camera system according to claim 10, further comprising adata line provided from one of (a) the camera modules and (b) theprinted circuit board, to a control device mounted separately from themount.
 12. The stereo camera system according to claim 1, furthercomprising a snap-in mechanism for a fixed-position installation of thecamera modules, situated in the mount.
 13. The stereo camera systemaccording to claim 12, wherein the mechanism is for the fixed-positioninstallation of a lens region of the camera modules.
 14. A stereo camerasystem in a motor vehicle having a windshield, the stereo camera systemcomprising: at least two camera modules; a mount in which the cameramodules are situated at a preselected lateral distance apart, the mountbeing cemented to an inside of the windshield, wherein the mount is onepiece and has two mounting regions, each of which holds one of thecamera modules and is rigidly connected to the other by a crosspiece andwherein the front of the crosspiece serves as a cementing region forfastening to the inside of the windshield; and means, provided in themount, for equalizing pressure of free spaces with respect to asurrounded space.
 15. The stereo camera system according to claim 14,wherein the surrounded space is a camera region.
 16. The stereo camerasystem according to claim 14, wherein the means for equalizing pressurecontains semi-permeable regions.
 17. The stereo camera system accordingto claim 16, wherein the semi-permeable regions include an air-permeableand moisture-impermeable material.
 18. The stereo camera systemaccording to claim 17, wherein the material is a microfiber textilematerial.